Stacked semiconductor structure and method

ABSTRACT

A device comprises a first chip comprising a first connection pad embedded in a first dielectric layer and a first bonding pad embedded in the first dielectric layer, wherein the first bonding pad comprises a first portion and a second portion, the second portion being in contact with the first connection pad and a second chip comprising a second bonding pad embedded in a second dielectric layer of the second chip, wherein the first chip and the second chip are face-to-face bonded together through the first bonding pad the second bonding pad.

This application is a continuation of U.S. patent application Ser. No.16/679,598, entitled “Stacked Semiconductor Structure and Method,” filedon Nov. 11, 2019, now U.S. Pat. No. 11,037,909, issued Jun. 15, 2021,which is a continuation of U.S. patent application Ser. No. 16/221,734,entitled “Stacked Semiconductor Structure and Method,” filed on Dec. 17,2018, now U.S. Pat. No. 10,510,730 issued Dec. 17, 2019, which is acontinuation of U.S. patent application Ser. No. 15/657,630, entitled“Stacked Semiconductor Structure and Method,” filed on Jul. 24, 2017,now U.S. Pat. No. 10,157,889 issued Dec. 18, 2018, which is acontinuation of U.S. patent application Ser. No. 15/018,490, entitled“Stacked Semiconductor Structure and Method,” filed on Feb. 8, 2016, nowU.S. Pat. No. 9,716,078 issued Jul. 25, 2017, which is a divisional ofU.S. patent application Ser. No. 14/250,024, entitled “StackedSemiconductor Structure and Method,” filed on Apr. 10, 2014, now U.S.Pat. No. 9,257,414 issued Feb. 9, 2016, which applications areincorporated herein by reference.

BACKGROUND

The semiconductor industry has experienced rapid growth due tocontinuous improvements in the integration density of a variety ofelectronic components (e.g., transistors, diodes, resistors, capacitors,etc.). For the most part, this improvement in integration density hascome from repeated reductions in minimum feature size, which allows morecomponents to be integrated into a given area. As the demand for evensmaller electronic devices has grown recently, there has grown a needfor smaller and more creative packaging techniques of semiconductordies.

As semiconductor technologies evolve, three-dimensional (3D) integratedcircuits (ICs) have emerged as an effective alternative to furtherreduce the physical size of a semiconductor chip. A 3D IC may comprise avariety of semiconductor dies stacked together. In particular, thesemiconductor dies may be bonded together through a plurality of microbumps and electrically coupled to each other through a plurality ofthrough vias. For example, active circuits such as logic, memory,processor circuits and the like are fabricated on different wafers andeach wafer die is stacked on top of another wafer die usingpick-and-place techniques. Through vias are thus used in the stackeddies for connecting dies.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross sectional view of a stacked semiconductordevice in accordance with various embodiments of the present disclosure;

FIG. 2 illustrates a perspective view of the stacked semiconductordevice shown in FIG. 1 after the stacked semiconductor device is mountedon a printed circuit board in accordance with various embodiments of thepresent disclosure;

FIG. 3 illustrates in detail a cross sectional view of the bondingstructure shown in FIG. 1 in accordance with various embodiments of thepresent disclosure;

FIG. 4 illustrates a cross sectional view of a first chip in accordancewith various embodiments of the present disclosure;

FIG. 5 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 4 after a first dielectric layer is deposited over thefirst chip in accordance with various embodiments of the presentdisclosure;

FIG. 6 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 5 after a plurality of openings are formed in the firstdielectric layer in accordance with various embodiments of the presentdisclosure;

FIG. 7 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 6 after a conductive material is filled in the openings inaccordance with various embodiments of the present disclosure;

FIG. 8 illustrates a cross sectional view of a second chip in accordancewith various embodiments of the present disclosure;

FIG. 9 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 8 after a second dielectric layer is deposited over thesecond chip in accordance with various embodiments of the presentdisclosure;

FIG. 10 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 9 after a plurality of openings are formed in the seconddielectric layer in accordance with various embodiments of the presentdisclosure;

FIG. 11 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 10 after a conductive material is filled in the openingsin accordance with various embodiments of the present disclosure;

FIG. 12 is a cross sectional view of the semiconductor device shown inFIG. 11 after the second chip is flipped and bonded on the first chip inaccordance with various embodiments of the present disclosure;

FIG. 13 is a cross sectional view of the stacked semiconductor deviceillustrated in FIG. 12 after a thinning process has been applied to thebackside of the second chip in accordance with various embodiments ofthe present disclosure; and

FIGS. 14-26 illustrate intermediate steps of fabricating another stackedsemiconductor device similar to that shown in FIG. 1 in accordance withvarious embodiments of the present disclosure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

FIG. 1 illustrates a cross sectional view of a stacked semiconductordevice in accordance with various embodiments of the present disclosure.As shown in FIG. 1 , a second chip 201 is stacked on top of a first chip101. A plurality of first bonding pads 120, 122, 124, 126 and 128 areformed in the first chip 101. Likewise, a plurality of second bondingpads 220, 222, 224, 226 and 228 are formed in the second chip 201.Furthermore, the bonding pads located at the second chip 201 (e.g.,bonding pad 220) are aligned face-to-face with their correspondingbonding pads located at the first chip 101 (e.g., bonding pad 120). Thefirst chip 101 and the second chip 201 are bonded together throughsuitable bonding techniques such as hybrid bonding. The hybrid bondingprocess will be described below with respect to FIG. 12 .

It should be noted that the number of bonding pads (e.g., first bondingpad 120 and second bonding pad 220) shown in FIG. 1 is merely anexample. A person skilled in the art will recognize that the stackedsemiconductor device 100 may accommodate any number of bonding pads.

As shown in FIG. 1 , the first chip 101 comprises a first substrate 102,first active circuits 104 and a first interconnect structure 106.Likewise, the second chip 201 comprises a second substrate 202, secondactive circuits 204 and a second interconnect structure 206. Inaddition, in order to bond the second chip 201 on the first chip 101, afirst dielectric layer 108 is formed over the first interconnectstructure 106 and a second dielectric layer 208 is formed over thesecond interconnect structure 206. The first chip 101 and the secondchip 201 are bonded together through the bonding pads formed in thedielectric layers. The detailed bonding process will be described belowwith respect to FIGS. 4-13 .

Throughout the description, the side of the semiconductor chips (e.g.,first chip 101) having active circuits (e.g., first active circuits 104)is alternatively referred to as the front side of the semiconductorchips. The opposite side is referred to as the backside of thesemiconductor chips.

In accordance with some embodiments, the first chip 101 and the secondchip 201 may be produced by different semiconductor foundries. Forexample, the first chip 101 is provided by a first foundry. As shown inFIG. 1 , the first foundry has mounted a plurality of first connectionpads 110, 112, 114, 116 and 118 on the front side of the first chip 101.A second foundry forms the plurality of first bonding pads 120, 122,124, 126 and 128 on the front side of the first chip 101 based upon thepattern of the first connection pads 110, 112, 114, 116 and 118.

The second chip 201 is provided by the second foundry. As describedabove, there may be a plurality of second bonding pads formed on thesecond chip 201. More particularly, the second chip 201 is configuredsuch that the second bonding pads (e.g., second bonding pad 220) arealigned face-to-face with their corresponding first bonding pads (e.g.,first bonding pad 120).

After the second chip 201 is stacked on the first chip 101, a pluralityof second connection pads 210 and 212 may be formed on a backside of thesecond chip 201. In some embodiments, both the first connection pads andthe second connection pads are formed of aluminum. As shown in FIG. 1 ,the second connection pads 210 and 212 are electrically coupled to thefirst connection pads 110, 112, 114, 116 and 118 through the bondingpads (e.g., bonding pads 220 and 120).

FIG. 2 illustrates a perspective view of the stacked semiconductordevice shown in FIG. 1 after the stacked semiconductor device is mountedon a printed circuit board in accordance with various embodiments of thepresent disclosure. As described above with respect to FIG. 1 , theremay be a plurality of second connection pads formed on the backside ofthe second chip 201. In some embodiments, the stacked semiconductordevice 100 is picked and mounted on the printed circuit board 200 asshown in FIG. 2 . The second connection pads on the second chip 201 maybe wire bonded to the input and output pads of the printed circuit board200 as shown in FIG. 2 .

It should be noted while FIG. 2 illustrates two stacked chips (e.g.,first chip 101 and second chip 201), this is merely an example.Likewise, the use of wire bonding shown in FIG. 2 is merely illustrativeand other approaches for electrically connecting the stacked chips arewithin the contemplated scope of the present disclosure.

One advantageous feature of having the stacked semiconductor device 100shown in FIGS. 1-2 is that the bonding structure of the stackedsemiconductor device 100 may be used to bond semiconductor chipsproduced by different semiconductor foundries. As such, the packagingand assembly cost may be reduced. Furthermore, the footprint of thesemiconductor device may be reduced by stacking two chips together.

FIG. 3 illustrates in detail a cross sectional view of the bondingstructure shown in FIG. 1 in accordance with various embodiments of thepresent disclosure. As shown in FIG. 3 , the second chip 201 maycomprise three bonding pads 326, 327 and 328. The bonding pad 326 iselectrically coupled to a metal line 322. The bonding pads 327 and 328are electrically coupled to a metal line 324. Metal lines 322 and 324are formed in the second interconnect structure 206 (shown in FIG. 1 ).

The first chip 101 may comprise three bonding pads 316, 317 and 318. Thebonding pads 316, 317 and 318 may be electrically coupled to a metalline 314 through a connection pad 312. The metal line 314 is formed inthe first interconnect structure 106 (shown in FIG. 1 ).

As shown in FIG. 3 , the distance between two adjacent first bondingpads (e.g., bonding pads 317 and 318) is defined as S1. The distancebetween two adjacent bonding pads (e.g., bonding pads 327 and 328) isdefined as S2. The width of the second bonding pads (e.g., bonding pad328) is defined as W2. The width of the first bonding pads (e.g.,bonding pad 318) is defined as W1. In some embodiments, W2 is greaterthan W1. W2 is less than 5 um. The ratio of S1 to W1 is greater than 4.The ratio of S2 to W2 is greater than 4.

FIGS. 4-13 illustrate intermediate steps of fabricating the stackedsemiconductor device shown in FIG. 1 in accordance with variousembodiments of the present disclosure. It should be noted that thefabrication steps as well as the stacked semiconductor device shown inFIGS. 4-13 are merely an example. A person skilled in the art willrecognize there may be many alternatives, variations and modifications.

FIG. 4 illustrates a cross sectional view of a first chip in accordancewith various embodiments of the present disclosure. The first chip 101comprises a first substrate 102, first active circuits 104, a firstinterconnect structure 106 and a plurality of connection pads as shownin FIG. 4 .

The first substrate 102 may be formed of silicon, although it may alsobe formed of other group III, group IV, and/or group V elements, such assilicon, germanium, gallium, arsenic, and combinations thereof. Thesubstrate may comprise a bulk substrate or a silicon-on-insulator (SOI)substrate.

In some embodiments, the first chip 101 may be from a standard waferhaving a thickness more than 100 um. In alternative embodiments, thefirst chip 101 may be of a thickness of about 770 um.

The first active circuits 104 are formed on the front side of the firstsubstrate 102. The first active circuit 104 may be any type of circuitrysuitable for a particular application. In some embodiments, the firstactive circuits 104 may include various n-type metal-oxide semiconductor(NMOS) and/or p-type metal-oxide semiconductor (PMOS) devices such astransistors, capacitors, resistors, diodes, photo-diodes, fuses and thelike. The first active circuits 104 may be interconnected to perform oneor more functions. The functions may include memory structures,processing structures, sensors, amplifiers, power distribution,input/output circuitry or the like. One of ordinary skill in the artwill appreciate that the above examples are provided for illustrativepurposes only to further explain applications of the present disclosureand are not meant to limit the present disclosure in any manner.

The first interconnect structure 106 may comprise a plurality ofinter-layer dielectric (ILD) layers and inter-metal dielectric (IMD)layers (not shown). The first interconnect structure 106 may furthercomprise a plurality of through vias (not shown).

In some embodiments, the first interconnect structure 106 may include anILD layer, an IMD layer, a metal line and a redistribution layer.Throughout the description, the dielectric layer in which contact plugsare formed is referred to as an ILD layer, and the dielectric layersover the ILD are referred to as IMD layers. The metal lines are formedin the IMD layers. The redistribution layer is formed over the IMDlayers.

This interconnect structure described above is merely an example, whichshould not unduly limit the scope of the claims. One of ordinary skillin the art would recognize many variations, alternatives, andmodifications. For example, the interconnect structure may comprise aplurality of IMD layers.

The ILD layer may be formed, for example, of a low-K dielectricmaterial, such as silicon oxide, phosphosilicate glass (PSG),borophosphosilicate glass (BPSG), fluorinated silicate glass (FSG),SiO_(x)C_(y), Spin-On-Glass, Spin-On-Polymers, silicon carbon material,compounds thereof, composites thereof, combinations thereof or the like,by any suitable method known in the art, such as spinning, chemicalvapor deposition (CVD), plasma chemical vapor deposition (PECVD) and/orthe like.

One or more IMD layers and the associated metal lines (not shown) areformed over the ILD layer. Generally, the one or more IMD layers and theassociated metal lines are used to interconnect the electrical circuitryto each other and to provide an external electrical connection. The IMDlayers are preferably formed of a low-K dielectric material, such asfluorosilicate glass (FSG) formed by PECVD techniques or high-densityplasma chemical vapor deposition (HDPCVD) or the like.

The metal lines may be formed of metal materials such as copper, copperalloys, aluminum, silver, gold, any combinations thereof and/or thelike. The metal lines may be formed by a dual damascene process,although other suitable techniques such as deposition, single damascenemay alternatively be used. The dual damascene process is well known inthe art, and hence is not discussed herein.

The redistribution layer may be a single material layer, or amulti-layered structure and may be made of metals such as titanium,titanium nitride, aluminum, tantalum, copper and combinations thereof.The redistribution layer may be made by any suitable method known in theart such as PVD, sputter, CVD, electroplating and/or the like.

One skilled in the art will recognize that the interconnect structuremay comprise more inter-metal dielectric layers and the associated metallines and plugs. In particular, the layers between the metallizationlayers may be formed by alternating layers of dielectric (e.g.,extremely low-k dielectric material) and conductive materials (e.g.,copper).

FIG. 5 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 4 after a first dielectric layer is deposited over thefirst chip in accordance with various embodiments of the presentdisclosure. The first dielectric layer 108 may be formed of any suitabledielectric materials such as a low-K dielectric and/or the like. Thefirst dielectric layer 108 may be formed by suitable depositiontechniques such as PECVD and/or the like. As shown in FIG. 5 , once thefirst dielectric layer 108 is deposited on the first chip 101, the firstconnection pads 110, 112, 114, 116 and 118 are embedded in the firstdielectric layer 108.

FIG. 6 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 5 after a plurality of openings are formed in the firstdielectric layer in accordance with various embodiments of the presentdisclosure. According to the locations of the connection pads 110, 112,114, 116 and 118, a plurality of openings 610, 612, 614, 616 and 618 areformed in the first dielectric layer 108. The openings may be formed byany suitable semiconductor patterning techniques such as an etchingprocess, a laser ablation process and/or the like. For example, theopenings may be formed by using photolithography techniques to depositand pattern a photoresist material on the first dielectric layer 108. Aportion of the photoresist is exposed according to the locations of theconnection pads shown in FIG. 6 . An etching process, such as ananisotropic dry etch process, may be used to create the openings in thefirst dielectric layer 108.

FIG. 7 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 6 after a conductive material is filled in the openings inaccordance with various embodiments of the present disclosure. Aconductive material may be filled in the openings. The conductivematerial may be copper, but can be any suitable conductive materials,such as copper alloys, aluminum, titanium, silver, any combinationsthereof and/or the like. The conductive material may be formed bysuitable techniques such as an electro-less plating process, CVD,electroplating and/or the like.

A planarization process may be performed to remove excess conductivematerials to form the first bonding pads as shown in FIG. 7 . Theplanarization process may be implemented by using suitable techniquessuch as grinding, polishing and/or chemical etching, a combination ofetching and grinding techniques.

In accordance with various embodiments, the planarization process may beimplemented by using a chemical mechanical polish (CMP) process. In theCMP process, a combination of etching materials and abrading materialsare put into contact with the top surface of the semiconductor deviceand a grinding pad (not shown) is used to grind away excess conductivematerials until the first dielectric layer 108 is exposed as shown inFIG. 7 .

FIG. 8 illustrates a cross sectional view of a second chip in accordancewith various embodiments of the present disclosure. As shown in FIG. 8 ,the second chip 201 comprises a second substrate 202, second activecircuits 204 and a second interconnect structure 206. The structure ofthe second chip 201 is similar to that of the first chip 101, and henceis not discussed in further detail herein to avoid repetition.

It should be noted that in some embodiments, the width of the secondinterconnect structure 206 is greater than the width of the secondactive circuits 204 as shown in FIG. 8 . In other words, the secondactive circuits 204 only occupy a portion of the top surface of thesecond substrate 202. Such an arrangement of the second active circuits204 helps to reduce the cost of the second chip 201.

FIG. 9 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 8 after a second dielectric layer is deposited over thesecond chip in accordance with various embodiments of the presentdisclosure. The formation process of the second dielectric layer 208 issimilar to that of the first dielectric layer 108 described above withrespect to FIG. 5 , and hence is not discussed again to avoidrepetition.

FIG. 10 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 9 after a plurality of openings are formed in the seconddielectric layer in accordance with various embodiments of the presentdisclosure. According to the locations of the first bonding pads shownin FIG. 7 , a plurality of openings 1010, 1012, 1014, 1016 and 1018 areformed in the second dielectric layer 208. The formation process of theopenings shown in FIG. 10 is similar to that of the openings shown inFIG. 6 , and hence is not discussed again to avoid repetition.

FIG. 11 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 10 after a conductive material is filled in the openingsin accordance with various embodiments of the present disclosure. Aconductive material may be filled in the openings. The conductivematerial may be copper, but can be any suitable conductive materials,such as copper alloys, aluminum, titanium, silver, any combinationsthereof and/or the like. The conductive material may be formed bysuitable techniques such as an electro-less plating process, CVD,electroplating and/or the like.

A planarization process is performed to remove excess conductivematerials to form the second bonding pads as shown in FIG. 11 . Theplanarization process may be implemented by using suitable techniquessuch as grinding, polishing and/or chemical etching, a combination ofetching and grinding techniques.

In accordance with various embodiments, the planarization process may beimplemented by using a CMP process. In the CMP process, a combination ofetching materials and abrading materials are put into contact with thetop surface of the semiconductor device and a grinding pad (not shown)is used to grind away excess conductive materials until the seconddielectric layer 208 is exposed as shown in FIG. 11 .

FIG. 12 is a cross sectional view of the semiconductor device shown inFIG. 11 after the second chip is flipped and bonded on the first chip inaccordance with various embodiments of the present disclosure. Once thesecond bonding pads are formed in the second chip 201, the second chip201 is flipped and further bounded on the first chip 101 as shown inFIG. 12 . In particular, the front side of the second chip 201 may faceup toward the front side of the first chip 101.

Various bonding techniques may be employed to achieve bonding betweenthe first chip 101 and the second chip 201. In accordance with anembodiment, suitable bonding techniques may include direct bonding,hybrid bonding and the like. In accordance with an embodiment, a hybridbonding process may be employed to bond the first chip 101 and thesecond chip 201 together. More particularly, through a bonding structuresuch a bonding chuck (not shown), the second chip 201 is stacked on topof the first chip 101 in a chamber (not shown). In particular, thebonding pads (e.g., bonding pad 220) of the second chip 201 are alignedface-to-face with their corresponding bonding pads (e.g., bonding pad120) located at the first chip 101.

A thermal process may be performed on the stacked chip structure. Such athermal process may lead to copper inter-diffusion. More particularly,the copper atoms of the bonding pads (e.g., bonding pads 120 and 220)acquire enough energy to diffuse between two adjacent bonding pads. As aresult, a homogeneous copper layer is formed between two adjacentbonding pads. Such a homogeneous copper layer helps the bonding pads(e.g., bonding pads 120 and 220) form a uniform bonded feature. Theuniform bonded feature establishes a conductive path between the firstchip 101 and the second chip 201. In addition, the uniform bondedfeature also provides a mechanical bond to hold the first chip 101 andthe second chip 201.

A post bonding anneal process may be performed on the stackedsemiconductor structure in a chamber with inert gases such as argon,nitrogen, helium and the like. The stacked semiconductor structure isbaked for approximately from thirty minutes to three hours at atemperature more than 300 degrees. As a result, the bonding pads of thefirst chip 101 and the bonding pads of the second chip 201 are reliablybonded together through the post bonding anneal process.

FIG. 13 is a cross sectional view of the stacked semiconductor deviceillustrated in FIG. 12 after a thinning process has been applied to thebackside of the second chip in accordance with various embodiments ofthe present disclosure. The backside of the second chip 201 undergoes athinning process. The thinning process can employ a mechanical grindingprocess, a chemical polishing process, an etching process and/or thelike. By employing the thinning process, in some embodiments, thebackside of the second chip 201 can be ground so that the second chip201 may have a thickness of approximately sub-100 um.

In addition, portions of the second substrate 202 have been removed inorder to mount the second connection pads on the second chip 201. Moreparticularly, second connection pads 210 and 212 are formed on thesecond interconnect structure 206 as shown in FIG. 13 . In someembodiments the second connection pads 210 and 212 are electricallycoupled to the first active circuits 104 through the bonding pads aswell as the interconnect structures.

FIGS. 14-26 illustrate intermediate steps of fabricating another stackedsemiconductor device similar to that shown in FIG. 1 in accordance withvarious embodiments of the present disclosure. The fabrication stepsshown in FIGS. 14-26 are similar to those shown in FIGS. 4-13 exceptthat there may be a tungsten connector formed between the connectionpads (e.g., connection pad 110) and the first bonding pads (e.g.,bonding pad 120). The fabrication steps shown in FIGS. 14-15 and 21-26are similar to those shown in FIGS. 4-5 and 8-13 , and hence are notdiscussed again herein to avoid repetition.

FIG. 16 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 15 after a plurality of openings are formed in the firstdielectric layer in accordance with various embodiments of the presentdisclosure. A plurality of openings 1610, 1612, 1614, 1616 and 1618 areformed in the first dielectric layer 108. The openings may be formed byany suitable semiconductor patterning techniques such as an etchingprocess, a laser ablation process and/or the like.

FIG. 17 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 16 after a conductive material is filled in the openingsin accordance with various embodiments of the present disclosure. Aconductive material may be filled in the openings. The conductivematerial may be tungsten, but can be any suitable conductive materials.The conductive material may be formed by suitable techniques such as CVDand/or the like.

A planarization process may be performed to remove excess conductivematerials to form tungsten connectors 1710, 1712, 1714, 1716 and 1718 asshown in FIG. 17 . The planarization process may be implemented by usingsuitable techniques such as grinding, polishing and/or chemical etching,a combination of etching and grinding techniques. In accordance withvarious embodiments, the planarization process may be implemented byusing a CMP process.

FIG. 18 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 17 after a dielectric material is deposited over thesemiconductor device in accordance with various embodiments of thepresent disclosure. The dielectric material may be the same as that ofthe first dielectric layer 108. The dielectric material may be depositedby suitable deposition techniques such as PECVD and/or the like.

FIG. 19 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 18 after a plurality of openings are formed in the firstdielectric layer in accordance with various embodiments of the presentdisclosure. According to the locations of the tungsten connectors, aplurality of openings 1910, 1912, 1914, 1916 and 1918 are formed in thefirst dielectric layer 108. The openings may be formed by any suitablesemiconductor patterning techniques such as an etching process, a laserablation process and/or the like.

FIG. 20 illustrates a cross sectional view of the semiconductor deviceshown in FIG. 19 after a conductive material is filled in the openingsin accordance with various embodiments of the present disclosure. Aconductive material may be filled in the openings 1910, 1912, 1914, 1916and 1918. The conductive material may be copper, but can be any suitableconductive materials, such as copper alloys, aluminum, titanium, silver,any combinations thereof and/or the like. The conductive material may beformed by suitable techniques such as an electro-less plating process,CVD, electroplating and/or the like.

A planarization process may be performed to remove excess conductivematerials to form the first bonding pads 2010, 2012, 2014, 2016 and 2018as shown in FIG. 20 . The planarization process may be implemented byusing suitable techniques such as grinding, polishing and/or chemicaletching, a combination of etching and grinding techniques. In accordancewith various embodiments, the planarization process may be implementedby using a CMP process.

In accordance with an embodiment, a device comprises a first chipcomprising a first connection pad embedded in a first dielectric layerand a first bonding pad embedded in the first dielectric layer, whereinthe first bonding pad comprises a first portion and a second portion,the second portion being in contact with the first connection pad and asecond chip comprising a second bonding pad embedded in a seconddielectric layer of the second chip, wherein the first chip and thesecond chip are face-to-face bonded together through the first bondingpad the second bonding pad.

In accordance with an embodiment, a device comprises a first chipcomprising a first connection pad embedded in a first dielectric layer,a first bonding pad embedded in the first dielectric layer and aconnector between the first connection pad and the first bonding pad anda second chip comprising a second bonding pad embedded in a seconddielectric layer of the second chip, wherein the first chip and thesecond chip are face-to-face bonded together through the first bondingpad and the second bonding pad.

In accordance with an embodiment, a device comprises a first chipcomprising a first connection pad embedded in a first dielectric layerand a first bonding pad embedded in the first dielectric layer, whereinthe first bonding pad comprises a first portion and a second portionhaving different widths and a second chip comprising a second bondingpad embedded in a second dielectric layer of the second chip, whereinthe first chip and the second chip are face-to-face bonded togetherthrough the first bonding pad and the second bonding pad.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A device comprising: a first chip comprising: afirst substrate; a first insulating layer; a first interconnectstructure interposed between the first insulating layer and the firstsubstrate; a first aluminum connection pad embedded in the firstinsulating layer; and a first copper bonding pad embedded in the firstinsulating layer, wherein the first aluminum connection pad directlycontacts the first copper bonding pad; and a second chip comprising: asecond substrate; a second interconnect structure; a second insulatinglayer, the second interconnect structure being interposed between thesecond insulating layer and the second substrate; and a second copperbonding pad embedded in the second insulating layer of the second chip,wherein the first chip and the second chip are face-to-face bondedtogether through the first copper bonding pad and the second copperbonding pad, wherein the first copper bonding pad and the second copperbonding pad comprise a single homogenous copper layer.
 2. The device ofclaim 1, further comprising an external connection pad contacting thesecond interconnect structure, wherein the second interconnect structureis interposed between the external connection pad and the first chip. 3.The device of claim 1, wherein a width of the first copper bonding padis different than a width of the second copper bonding pad.
 4. Thedevice of claim 1, wherein a width of at least a portion of the firstaluminum connection pad is different than a width of the first copperbonding pad.
 5. The device of claim 1, wherein the first chip and thesecond chip are attached to a printed circuit board.
 6. The device ofclaim 1, wherein the first insulating layer comprises a first sub-layerand a second sub-layer, wherein the first sub-layer has a surface levelwith an interface between the first aluminum connection pad and thefirst copper bonding pad.
 7. A device comprising: a first structurecomprising: a first substrate; a first insulating layer; a firstinterconnect structure interposed between the first insulating layer andthe first substrate; and a first aluminum connection pad embedded in thefirst insulating layer; and a second structure comprising: a secondsubstrate; a second interconnect structure; and a second insulatinglayer, the second interconnect structure being interposed between thesecond insulating layer and the second substrate, the second insulatinglayer being directly bonded to the first insulating layer; and a firstcopper bonding feature extending from the first aluminum connection padto the second interconnect structure.
 8. The device of claim 7, whereinthe first substrate and the second substrate each comprise activecircuits, wherein the first substrate and the second substrate arebonded in a face-to-face configuration.
 9. The device of claim 7,wherein at least a portion of the first aluminum connection pad isdifferent than a width of the first copper bonding feature.
 10. Thedevice of claim 7, further comprising an external connection padcontacting the second interconnect structure, wherein the secondinterconnect structure is interposed between the external connection padand the first structure.
 11. The device of claim 10, wherein an uppersurface of the external connection pad is lower than an upper surface ofthe second substrate.
 12. The device of claim 7, wherein the firstinsulating layer contacts a horizontal surface and a vertical surface ofthe first aluminum connection pad.
 13. The device of claim 7, furthercomprising a second copper bonding feature contacting the first aluminumconnection pad.
 14. The device of claim 7, further comprising a printedcircuit board, wherein the first structure and the second structure aremounted on a printed circuit board.
 15. A device comprising: a firstsubstrate including a first insulating layer, a first conductive layerin the first insulating layer, a first metal layer in the firstinsulating layer, and a second metal layer provided between the firstmetal layer and the first conductive layer, wherein the second metallayer is an aluminum metal layer, wherein the first metal layer is afirst copper metal layer; and a second substrate being in contact withthe first substrate, the second substrate including: a second insulatinglayer directly bonded to the first insulating layer, and a third metallayer provided in the second insulating layer, the third metal layerbeing in physical contact with the first metal layer, wherein the thirdmetal layer is a second copper metal layer, wherein the first insulatinglayer and the second insulating layer directly contacts the third metallayer.
 16. The device of claim 15, wherein the first metal layer and thethird metal layer form a homogenous layer.
 17. The device of claim 15,wherein the second substrate further comprises: a semiconductorsubstrate; an interconnect structure interposed between thesemiconductor substrate and the second insulating layer; and an externalconnection pad contacting the interconnect structure, wherein theinterconnect structure is interposed between the external connection padand the first insulating layer.
 18. The device of claim 15, wherein thefirst substrate and the second substrate are bonded face-to-face. 19.The device of claim 15, wherein a width of the first metal layer isdifferent than a width of the third metal layer.
 20. The device of claim15, wherein the second substrate further includes a fourth metal layer,wherein the fourth metal layer is a second aluminum metal layer.